1. Field
An aspect of the present invention relates to a semiconductor device and a manufacturing method thereof, and more particularly, to a semiconductor device having a three-dimensional structure and a manufacturing method thereof.
2. Discussion of Related Art
A nonvolatile memory device is a memory device in which stored data are maintained when a power supply is interrupted. As integration of a two-dimensional memory device in which memory cells are formed in a single layer on a silicon substrate reaches its limits, there has recently been proposed a three-dimensional nonvolatile memory device in which memory cells are vertically stacked on a silicon substrate.
The three-dimensional nonvolatile memory device includes interlayer insulating layers and word lines, which are alternately stacked, and channel layers penetrating the interlayer insulating layers and the word lines. Memory cells are stacked along the channel layers. Contact plugs are respectively connected to the stacked word lines, thereby selectively driving desired memory cells.
However, to implement such a structure, contact plugs having various depths should be formed which results in using a complicated manufacturing process. For example, in a process of forming a contact plug, it is difficult to adjust the depth of a contact hole due to a step difference of an Interlayer insulating layer. Therefore, the contact plug may penetrate a word line, thereby causing a bridge. Alternatively, the contact plug may not reach the word line, and therefore, a process defect may occur.